This invention relates to a process for the production of pastas by extrusion and to an extrusion unit for carrying out this process.
A conventional process for the production of pastas comprises thoroughly mixing a cereal flour and a suitable quantity of water in a first unit to obtain a pasta in which hydration of the starch and gluten has already started.
In a second stage and in a second unit, the paste obtained is subjected to a mechanical kneading treatment during which the gluten network leading to an elastic product is established.
In a third stage and in a third unit, the paste obtained is subjected either to extrusion in a unit consisting of a screw extruder accommodated in a casing terminating in a dye, which gives the product its final shape, or to rolling.
The first stage can last 20 to 30 minutes, the second stage lasting approximately 10 minutes.
Various attempts have been made to shorten the duration of the process.
Thus, it has been proposed to carry out the first stage in a high-speed mixer. This reduces the duration of this stage to less than 30 seconds.
In addition it has been proposed, Cf. for example PCT Patent Application Publication NO. WO 90/05452, to carry out the first two stages in a single unit consisting of two interengaging endless screws rotating in the same direction and accommodated in a casing.
In this document, it is thus proposed to make a paste, for example intended to be subsequently extruded by a screw extruder to give pastas, the mixing and kneading phases being carried out in a single unit over period of less than 1 minute.
In this process, the water content of the paste after the addition of water is between 25% and 40% by weight and the product is kept at a temperature of 40.degree. to 50.degree. C. to avoid cooking which would produce irreversible changes in the product.
Although this apparatus and this process effectively enable the mixing and kneading time to be substantially reduced, it nevertheless remains that the paste obtained still has to be transferred to a separate extrusion unit.
Thus, on the one hand, the production process is not continuous and, on the other hand, the reduction in the production time is not optimal.